Since Windows 10's launch in 2015, Microsoft has made a concerted effort to get people using older versions of Windows to upgrade.

Microsoft ran a year-long free Windows 10 upgrade program for Windows 7 and 8.1 users until July 2016, and has since concentrated on persuading businesses to begin the transition to its flagship OS. The latest figures from Microsoft showed there were 600 million active monthly users of Windows 10.

"This is a breakthrough for Microsoft," said Aodhan Cullen, CEO of StatCounter.

"Windows 10 was launched at the end of July 2015 and Microsoft will be pleased to have put its Windows 8 experience behind it. However, Windows 7 retains loyalty especially amongst business users."

Cullen said Microsoft will want to avoid a repeat of what happened with Windows XP, where there were instances of organizations leaving the transition until just before support ended in 2014, with some big names, such as the US Navy, paying millions to stick with XP after Extended Support ended.

"Microsoft will be hoping that it can replace it [Windows 7] a lot quicker than XP, launched back in August 2001, which only fell below 5% usage worldwide in June of 2017," said Cullen.

StatCounter's desktop OS figures vary widely according to the region, with Windows 10 overtaking 7 in North America in January 2017, and in the UK in June 2016.